<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    /* .parent{
        border: 2px solid #333;
        width: 100px;
        height: 100px;
        display: flex;
        justify-content: center;
        align-items: center;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: yellow;
    } */

    /* .parent{
        border: 2px solid #333;
        width: 100px;
        height: 100px;
        position: absolute;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: yellow;
        position: relative;
        left: 30px;
        top: 30px;
    } */

    .parent{
        border: 2px solid #333;
        width: 100px;
        height: 100px;
    }
    .test{
        width: 40px;
        height: 40px;
        background-color: yellow;
        margin: 30px;
    }  
</style>
<body>
    <div class="parent">
        <div class="test">

        </div>
    </div>

</body>

</html>